Bis(tetrahydro-indenyl) metallocenes as olefin-polymerization-catalyst

ABSTRACT

A new class of bridged bis(tetrahydro-indenyl)metallocenes of formula (I),                    
     wherein M is Zr or Hf; X are monoanionic sigma ligands; (ZR 1   i ) j  is a divalent group bridging the two tetrahydro-indenyl residues; R 2  and R 3  are halogen, alkyl, cycloalkyl, aryl, alklyaryl or arylalkyl radicals; p is 0-3; i is 1 or 2; j is 1-4; m is 1-2; and n is 0-8. Furthermore, catalysts systems for olefin polymerization containing them are described.

FIELD OF THE INVENTION

The present invention relates to new bridgedbis(tetrahydro-indenyl)metallocenes, to the corresponding ligands and tocatalysts for the polymerization of olefins containing them.

PRIOR ART DISCLOSURE

Stereorigid chiral metallocene compounds possessing two bridgedcyclopentadienyl groups condensed to a C₅-C₇ ring are well known in thestate of the art and are mainly used as catalytic components in olefinpolymerization processes; in particular, metallocene compoundspossessing two bridged indenyl or 4,5,6,7-tetrahydro-indenyl groups arewidely used in the preparation of stereoregular polyolefins.

The numbering of the substituents on the indenyl group, to whichreference is made in the present application, in accordance with theIUPAC nomenclature, is the following:

In the bridged indenyl and tetrahydro-indenyl metallocene compoundsknown in the state of the art, the indenyl groups are linked together bydivalent radicals generally linked to the 1 position of said indenylgroups, and therefore, the common indenyl metallocenes are 1-indenylcompounds.

For example, the European patent application EP 0 485 823 describes aclass of bridged bis(1-indenyl)metallocenes, wherein the indenyl groupshave a substituent other than hydrogen in the 2 position and are bridgedin the 1 position by means of a bridge containing 1 or more carbon atoms(e.g. an ethylene or isopropylidene group) or containing heteroatoms(e.g. a dimethyl-silyl or a diphenyl-silyl group).

European patent application EP 0 485 821 describes a class of bridgedbis(4,5,6,7-tetrahydro-inden-1-yl)metallocenes, bearing a substituent inthe 2 position and bridged in the 1 position by means of an ethylene,isopropylidene, dimethyl-silyl or diphenyl-silyl group.

The European patent application EP 0 372 414 describes a very broadclass of bridged or unbridged metallocenes; among the many metallocenesexemplified, two specific bis-indenyl metallocene compounds arereported, wherein the ethylene group bridging the indenyl groups islinked to the 1 position of one indenyl group and to the 2 position ofthe other indenyl group (formulae II-1 and II-2, on page 5 of saidapplication). No tetrahydro-indenyl derivatives are mentioned.

The International patent application WO 94/11406 describes a very broadclass of metallocene compounds of formula R′Ind—M—(Cp)Q_(k), wherein:Ind is an indenyl group; R′ is a substituent, other than hydrogen,linked in the 2 position of said indenyl group; Cp is a cyclopentadienylgroup; M is a transition metal belonging to group 3, 4, 5 or 6 of thePeriodic Table of Elements; and Q is a sigma-ligand of the metal M, kbeing an integer linked to the valence of M. Among the huge plethora ofembodiments envisaged in the reported general formula, R′ can form abridge between the 2 position of the Ind group and the Cp group of theabove formula. Even in this document, there is no reference totetrahydro-indenyl derivatives. Moreover, the bis-indenyl zirconocenestested in the working examples shows very poor activities in ethylene(co)polymerization, leading to products with unsatisfactory molecularweights.

SUMMARY OF THE INVENTION

The Applicant has now unexpectedly found a new class of metallocenes,particularly active as catalyst components for the polymerization ofolefins; said metallocenes are characterized by the presence of two4,5,6,7-tetrahydro-indenyl groups linked in the 2 position by means of adivalent bridging group. Therefore, an object of the present inventionis a bridged bis(tetrahydro-indenyl)metallocene of formula (I):

wherein:

M is a transition metal belonging to group 3, 4, 5, 6 or to thelanthanide or actinide groups of the Periodic Table of the Elements (newIUPAC notation);

the substituents X, the same or different from each other, aremonoanionic sigma ligands selected from the group consisting ofhydrogen, halogen, —R, —OR, —OSO₂CF₃, —OCOR, —SR, —NR₂ and —PR₂ groups,wherein the R substituents are linear or branched, saturated orunsaturated, C₁-C₁₀ alkyl, C₆-C₂₀ cycloalkyl, C₆-C₁₀ aryl, C₇-C₂₀alkylaryl or C₇-C₂₀ arylalkyl radicals, optionally containing one ormore atoms belonging to groups 13-17 of the Periodic Table of theElements (new IUPAC notation), such as B, N, P, Al, Si, Ge, O, S and Fatoms, and two R substituents may form a 5-7-membered ring; preferably,the substituents X are the same;

(ZR¹ _(i))_(j) is a divalent group bridging the two tetrahydro-indenylresidues, Z being selected from the group consisting of C, Si, Ge, N andP; the substituents R¹, the same or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals, optionally containingone or more atoms belonging to groups 13-17 of the Periodic Table of theElements (new IUPAC notation), such as B, N, P, Al, Si, Ge, O, S and Fatoms;

the substituents R² and R³, the same or different from each other, areselected from the group consisting of halogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals, optionally containingone or more atoms belonging to groups 13-17 of the Periodic Table of theElements (new IUPAC notation; such as B, N, P, Al, Si, Ge, O, S and Fatoms), —OR, —SR, —NR₂, N-pyrrolyl, N-indolyl, —PR₂, —BR₂ and —SiR₃groups, wherein the R substituents have the meaning reported above; ortwo adjacent R³ substituents form a ring having from 4 to 8 carbonatoms;

p is an integer ranging from 0 to 3, being equal to the oxidation stateof the metal M minus 2;

i is 1 or 2; j is an integer ranging from 1 to 4; m is an integerranging from 0 to 2; n is an integer ranging from 0 to 8.

Another object of the present invention is a catalyst for thepolymerization of olefins comprising the product obtainable bycontacting:

(A) one or more bridged bis(tetrahydro-indenyl)metallocene of formula(I), as described above; and

(B) a suitable activating cocatalyst.

Furthermore, the present invention provides a process for thepolymerization of olefins comprising the polymerization reaction of oneor more olefinic monomers in the presence of a catalyst as describedabove.

It is another object of the present invention a ligand of formula (II):

or a double bond isomer thereof, wherein the double bonds of thecyclopentadienyl rings can be in any of the allowed positions, Z, R¹,R², R³, i, j, m and n having the meaning reported above, with theproviso that, when m is 0, then n is different from 0.

BRIEF DESCRIPTION OF THE DRAWINGS

In FIG. 1 are reported the curves obtained by GPC analysis of thepolymers of Example 11(A), Comparative Example 4(B) and Example 12(C).Said analysis was carried out with a WATERS 150 instrument, intrichlorobenzene at 135° C.

DETAILED DESCRIPTION OF THE INVENTION

The bridged bis(tetrahydro-indenyl)metallocenes of formula (I), thecatalysts for the polymerization of olefins containing them and theligands of formula (II), according to the present invention, will bebetter described in the following detailed description.

It is an object of the present invention a bridgedbis(tetrahydro-indenyl)metallocene of formula (I), as reported above,wherein the metal M preferably belongs to group 4 of the Periodic Tableof the Elements, and more preferably is Zr or Hf.

The X substituents are preferably Cl, Br or methyl, and are preferablythe same.

The divalent bridge (ZR¹ _(i))_(j) is preferably selected from the groupconsisting of CR¹ ₂, SiR¹ ₂, GeR¹ ₂, NR¹, PR¹ and (CR¹ ₂)₂, R¹ havingthe meaning reported above. More preferably, said divalent bridge isSi(CH₃)₂, SiPh₂, CH₂, (CH₂), or C(CH₃)₂, and even more preferably it isCH₂. The variable i is 1 or 2, and more specifically it is 1 when Z is Nor P, and it is 2 when Z is C, Si or Ge; j ranges from 1 to 4 and, whenj>1, the atoms Z can be the same or different from each other, such asin the divalent bridges —CH₂—Si(CH₃)₂—, —CH₂—O— and —CH₂—S—.

R² is preferably selected from the group consisting of methyl, ethyl,n-propyl, i-propyl, n-butyl, t-butyl, phenyl, benzyl andtrimethyl-silyl. The choice of the preferred R² depends also on thenature of the final polymer, as will be evident from what reportedbelow.

R³ is preferably selected form the group consisting of halogen, methyl,ethyl, n-propyl, i-propyl, n-butyl, t-butyl, phenyl and benzyl.

The variable m ranges from 0 to 2; the variable n ranges from 0 or 8.

Non-limiting examples of bridged bis(tetrahydro-indenyl)metallocenescorresponding to formula (I), according to the present invention are:

rac- andmeso-methylene-bis(1-methyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-methylene-bis(1-ethyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac-methylene-bis(1-t-butyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-methylene-bis(1-trimethylsilyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-methylene-bis(1-phenyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-isopropylidene-bis(1-methyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-isopropylidene-bis(1-ethyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac-isopropylidene-bis(1-t-butyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-isopropylidene-bis(1-trimethylsilyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-isopropylidene-bis(1-phenyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-dimethylsilyl-bis(1-methyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-dimethylsilyl-bis(1-ethyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac-dimethylsilyl-bis(1-t-butyl-4,5,6,7-tetrahydroinden-2yl)zirconiumdichloride,

rac- andmeso-dimethylsilyl-bis(1-trimethylsilyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-dimethylsilyl-bis(1-phenyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-ethylene-bis(1-methyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-ethylene-bis(1-ethyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- ethylene-bis(1-t-butyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-ethylene-bis(1-trimethylsilyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-ethylene-bis(1-phenyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

methylene-bis(1,3-dimethyl-4,5,6,7-tetrahydroinden-2yl)zirconiumdichloride,

methylene-bis(4,7-dimethyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-methylene-bis(4-phenyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

rac- andmeso-methylene-bis(4-terbutyl-7-methyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride,

and the corresponding zirconium dimethyl metallocenes.

The bridged bis(tetrahydro-indenyl)metallocenes of formula (I) can beprepared by reaction of the corresponding ligands of formula (II) firstwith a compound capable of forming a delocalized anion on thecyclopentadienyl ring, and then with a compound of formula MX_(p+2),wherein M, X and p are defined as above, according to common proceduresknown in the state of the art.

When, in the metallocene of formula (I), one or more X groups are otherthan halogen, it is necessary to substitute one or more halogens Z ofthe metallocene halide, obtained as reported above, with one or moresubstituents X other than halogen. The substitution reaction can becarried out by standard procedures, for example, when the substituents Xare alkyl groups, by reacting the metallocene halide with alkylmagnesiumhalides (Grignard reagents) or with alkyllithium compounds.

According to another embodiment, when in formula (I) the X groups havethe meaning of —R, as defined above, the methylene-bridged metallocenesof the invention can be obtained by reacting directly a ligand offormula (II) with at least one molar equivalent of a compound of formulaMX_(s), in the presence of at least (p+2) molar equivalents of asuitable alkylating agent, wherein R, M and X have the meaning reportedabove and s is an integer corresponding to the oxidation state of themetal M and ranges from 3 to 6. Said alkylating agent can be an alkalineor alkaline-earth metal, such as LiR or MgR₂, or a Grignard reagent,such as RMgCl or RMgBr, as described in WO 99/36427 (priority Europeanapp. no. 98200077.0), in the name of the same Applicant.

According to a preferred embodiment, the bridgedbis(tetrahydro-indenyl)metallocenes of formula (I) are prepared byhydrogenation of the corresponding bis-indenyl metallocenes. Thehydrogenation of bis-indenyl metallocenes to the correspondingtetrahydro-indenyl derivatives is preferably carried out in organicsolvents, such as CH₂Cl₂ or DME, at a temperature of 20-70° C, under aH₂ pressure of 1-200 bar, for a period ranging from 15 minutes to 24hours, in the presence of a hydrogenation catalyst, such as Pt, PtO₂, Pdor other catalysts known in the state of the art.

The bis-indenyl metallocenes can be prepared from the correspondingbis-indenyl ligands, according to procedures known in the state of theart.

When the divalent bridge (ZR¹ _(i))_(j) is —CH₂—, the correspondingbis-indenyl ligands can be prepared by reacting formaldehyde with anindene of formula (IV):

wherein the R²; R³ have the meaning reported above, n ranges from 0 to4, and q is 0 or 1, as described in the co-pending European app. No.98203906.7, in the name of the same Applicant. When the divalent bridge(ZR¹ _(i))_(j) is —CH₂CH₂—, the corresponding bis-indenyl ligands can beprepared as described in EP 0 942 011 (priority European app. no.98200728.8), in the name of the same Applicant.

When the divalent bridge (ZR¹ _(i))_(j) is Me₂Si<, the correspondingbis-indenyl ligands can be prepared by reacting the lithium salt of4,5,6,7-tetrahydroindene with dimethyldichlorosilane, according tomethods known in the state of the art (W. Mengele et al.,Organometallics, 12:1931-1935, 1993).

It is another object of the invention a ligand having formula (II) asreported above. Said ligands can be prepared by reacting an indene offormula (III):

or a double bond isomer thereof, wherein the double bonds of thecyclopentadienyl rings can be in any of the allowed positions, thevariables R², R³ and n having the meaning reported above and q being 0or 1, with a suitable base so to produce the corresponding anion, andthen reacting said anion with (ZR¹ _(i))_(j)X′₂, wherein (ZR¹ _(i))_(j)has the meaning reported above and X′ is halogen. For instance, when(ZR¹ _(i))_(j) is Me₂Si<, the procedure described by W. Mengele et al.(Organometallics, 12:1931-1935, 1993) can be followed.

When in the ligand of formula (II) m is ≠0, the substituents R² can alsobe introduced on the cyclopentadienyl ring by reacting the correspondingligand of formula (II) wherein m=0 with a suitable amount of adeprotonating agent R′MgBr, R′MgCl or R′_(k)B, wherein R′ can have thesame meaning of R³, B is an alkaline or alkaline-earth metal, and k is 1or 2, and then with a suitable amount of an alkylating agent R²X′,wherein R² has the meaning reported above and X′ is halogen.

The bridged bis(tetrahydro-indenyl)metallocenes according to the presentinvention can be advantageously used as catalytic components for thepolymerization of olefins. Thus, another object of the present inventionis a catalyst system for the polymerization of olefins, comprising theproduct obtainable by contacting:

(A) one or more bridged bis(tetrahydro-indenyl)metallocenes of formula(I), as described above, and

(B) a suitable activating cocatalyst.

Activating cocatalysts suitable as component (B) in the catalysts of theinvention are linear, branched or cyclic alumoxanes, containing at leastone group of the type:

wherein the substituents R⁴, the same or different from each other, area linear or branched, saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl, C₇-C₂₀ arylalkyl radicals,optionally containing Si and Ge atoms, or R⁴ is a group —O—Al(R⁴)₂. R⁴is preferably methyl, ethyl, isobutyl or 2,4,4-trimethyl-pentyl.

Examples of alumoxanes suitable as activating cocatalysts in thecatalysts according to the present invention are methylalumoxane (MAO),tetra-isobutyl-alumoxane (TIBAO), tetra-2,4,4-trimethylpentylalumoxane(TIOAO) and tetra-2-methyl-pentylalumoxane. Mixtures of differentalumoxanes can also be used.

Activating cocatalysts suitable as component (B) in the catalysts of theinvention are also the products of the reaction between water and anorganometallic aluminum compound, preferably of formula AlR⁵ ₃ or Al₂R⁵₆, wherein R⁵ has the meaning reported above. Particularly suitable arethe organometallic aluminum compounds of formula (II) described in EP 0575 875 and those of formula (II) described in WO 96/02580. Moreover,suitable cocatalysts are the ones described in WO 99/21899 (priorityEuropean app. no. 97203332.8) and in the European app. no. 99203110.4.Non-limiting examples of organometallic aluminum compounds of formulaAlR⁴ ₃ or Al₂R⁴ ₆ are: tris(methyl)aluminum, tris(isobutyl)aluminum,tris(isooctyl)aluminum, bis(isobutyl)aluminum hydride,methyl-bis(isobutyl)aluminum, dimethyl(isobutyl)aluminum,tris(isohexyl)aluminum, tris(benzyl)aluminum, tris(tolyl)aluminum,tris(2,4,4-trimethylpentyl)aluminum, bis(2,4,4-trimethylpentyl)aluminumhydride, isobutyl-bis(2-phenyl-propyl)aluminum,diisobutyl-(2-phenyl-propyl)aluminum,isobutyl-bis(2,4,4-trimethyl-pentyl)aluminum.diisobutyl-(2,4,4-trimethyl-pentyl)aluminum,tris(2,3-dimethyl-hexyl)aluminium, tris(2,3,3-trimethyl-butyl)aluminium,tris(2,3-dimethyl-butyl)aluminium, tris(2,3-dimethyl-pentyl)aluminium,tris(2-methyl-3-ethyl-pentyl)aluminium,tris(2-ethyl-3-methyl-butyl)aluminium,tris(2-ethyl-3-methyl-pentyl)aluminium,tris(2-isopropyl-3-methyl-butyl)aluminium andtris(2,4-dimethyl-heptyl)aluminium.

Particularly preferred aluminum compounds are trimethylaluminum (TMA),tris(2,4,4-trimethylpentyl)aluminum (TIOA), triisobutylaluminum (TIBA),tris(2,3,3-trimethyl-butyl)aluminium andtris(2,3-dimethyl-butyl)aluminium.

Mixtures of different organometallic aluminum compounds and/oralumoxanes can also be used.

The molar ratio between aluminum and the metal M of themethylene-bridged metallocene is preferably comprised between about 10:1and about 50,000:1, and preferably between about 100:1 and about4,000:1.

In the catalyst system according to the present invention, both saidmethylene-bridged metallocene and said alumoxane can be pre-reacted withan organometallic aluminum compound of formula AlR⁴ ₃ or Al₂R⁴ ₆,wherein the R⁴ substituents have the meaning reported above.

Further activating cocatalysts suitable as component (B) in thecatalysts of the invention are those compounds capable of forming analkylmetallocene cation; preferably, said compounds have formula Y⁺Z⁻,wherein Y⁺ is a Broensted acid capable of donating a proton and ofreacting irreversibly with a substituent X of the compound of formula(I), and Z⁻ is a compatible non-coordinating anion, capable ofstabilizing the active catalytic species which result from the reactionof the two compounds, and which is sufficiently labile to bedisplaceable by an olefinic substrate. Preferably, the Z⁻ anioncomprises one or more boron atoms. More preferably, the anion Z⁻ is ananion of formula BAr₄ ⁽⁻⁾, wherein the Ar substituents, the same ordifferent from each other, are aryl radicals such as phenyl,pentafluorophenyl, bis(trifluoromethyl)phenyl.Tetrakis-pentafluorophenyl-borate is particularly preferred. Moreover,compounds of formula BAr₃ can be conveniently used.

The catalysts of the present invention can also be used on inertsupports. This is achieved by depositing the methylene-bridgedmetallocene (A), or the product of its reaction with the activatingcocatalyst (B), or the component (B) and then the metallocene (A), on asuitable inert support, such as silica, alumina, magnesium halides,olefin polymers or prepolymers, such as polyethylenes, polypropylenes orstyrene-divinylbenzene copolymers.

The thus obtained supported catalyst system, optionally in the presenceof alkylaluminum compounds, either untreated or pre-reacted with water,can be usefully employed in gas-phase polymerization processes.

The present invention also provides a process for the homo orcopolymerization of olefins, comprising the polymerization reaction ofone or more olefinic monomers in the presence of a catalyst system asdescribed above. Representative examples of olefinic monomers which maybe used in the polymerization process of the invention are ethylenealpha-olefins such as propylene, 1-butene, 1-hexene, 4-methyl-1-penteneand 1-octene, and non-conjugated diolefins such as 1,5-hexadiene.

The catalyst systems of the invention are particularly advantageous inethylene and propylene homopolymerizations; in fact, by changing thesubstitution patterns of the bridged bis(tetrahydro-indenyl)metallocenesof the invention it is possible to obtain in high yields, attemperatures of industrial interest, polyethylenes and polypropyleneshaving intrinsic viscosity (I.V.) ranging from very low to high values.Therefore, an advantage of the metallocenes of the invention is thatthey allow polymers having a wide range of molecular weights to beobtained. From propylene homopolymerization, by using the metallocenesof formula (I) wherein M is Zr, according to the invention, it ispossible to obtain atactic propylene oligomers, terminated withvinylidene end-groups, which are particularly useful as lubricants,functionalizable monomers and chemical intermediates. By using themetallocenes of formula (I) wherein M is Hf, atactic polypropylenehaving higher molecular weight values are obtainable.

From ethylene homopolymerization, it is possible to obtain linearα-olefins having a Pn (Number Average Degree of Polymerization) rangingfrom 50 to 500, and preferably from 80 to 350; these α-olefins have morethan 90% of terminal vinyl unsaturations (on the total number ofterminal vinyl and vinylidene unsaturations). By varying thesubstitution pattern on the catalysts according to the invention, and inparticular by using methylene-bridgedbis(1-methyl-4,5,6,7-tetrahydro-inden-2-yl)metallocenes, it is possibleto obtain linear α-olefins having a percentage of terminal vinylunsaturations ≧95%, preferably ≧98%, thus providing useful α-olefinic PEwaxes. Said α-olefins are linear, having a number of total branchespreferably lower than 1/100 carbon atoms, and more preferably lower than0.1/100C. These α-olefins are particularly useful as polymerizationmonomers and chemical intermediates.

Moreover, the catalyst systems of the invention are particularlyadvantageous in the copolymerization of ethylene and propylene, becausethey allow to obtain copolymers in high yields, having a broad range ofcomonomer content (ranging from 5 to 70% wt.), having I.V. valuesranging 0.6 to 4 dl/g.

The polymerization process can be carried out in the liquid phase,optionally in the presence of inert hydrocarbon solvents, or in the gasphase. The hydrocarbon solvent can be either aromatic, such as toluene,or aliphatic, such as propane, hexane, heptane, isobutane andcyclohexane.

The polymerization temperature is generally comprised between −100° C.and +150° C., and more particularly between 50° C. and 100° C. The loweris the polymerization temperature, the higher are the molecular weightsof the polymers obtained.

The molecular weight of the polymers can be further varied by changingthe type or the concentration of the catalytic components or by usingmolecular weight regulators, for example hydrogen.

The molecular weight distribution can be varied by using mixtures ofdifferent metallocenes, or by carrying out the polymerization in severalsteps, that differ with respect to the temperatures of polymerizationand/or the concentrations of molecular weight regulators.

An advantageous embodiment of the process for the polymerization ofolefins, according to the present invention, is the use of a metalloceneof formula (I) in combination with other metallocenes known in the stateof the art, in order to produce polyethylenes with a well-definedbimodal distribution. More specifically, a metallocene of formula (I)able to produce PE waxes having low molecular weight, such asmethylene-bis(1-methyl-2-tetrahydro-indenyl)metallocenes, may be used inmixture with one or more metallocenes known in the state of the art,able to yield polyethylenes having high molecular weights; by combiningthe above metallocenes, it is possible to obtain bimodal or multimodalpolyethylenes which, despite the presence of the PE wax fraction of theinvention (having very low molecular weight), do not have significantamounts of extractables.

The polymerization yields depend on the purity of the metallocenecompound of the catalyst.

The metallocene compounds obtained by the process of the invention canbe used as they are, or they can undergo purification treatments.

The components of the catalyst can be brought into contact with eachother prior to polymerization. The duration of contact is generallybetween 1 and 60 minutes, preferably between 5 and 20 minutes. Thepre-contact concentrations for the metallocene component (A) are between1 and 10⁻⁸ mole/l, whereas for component (B) they are between 10 and10⁻⁸ mole/l. Precontact is generally effected in the presence of ahydrocarbon solvent and, if suitable, in the presence of small amountsof monomer.

The following experimental examples are given for illustrative and notlimiting purposes.

General Procedures and Characterizations

All operations were performed under nitrogen by using conventionalSchlenk-line techniques. Solvents were purified by degassing with N₂ andpassing over activated (8 hours, N₂ purge, 300° C.) Al₂O₃, and storedunder nitrogen.

The metallocenes and the ligands thereof were characterized by thefollowing methods:

¹H-NMR

All compounds were analyzed on an AC 200 Bruker spectrometer by ¹H NMR(CDCl₃, referenced against the peak of residual CHCl₃ at 7.25 ppm, orCD₂Cl₂, referenced against the peak of residual CHDCl₂ at 5.35 ppm). AllNMR solvents were dried over LiAlH₄, P₂O₅ or CaH₂ and distilled beforeuse. Preparation of the samples was carried out under nitrogen usingstandard inert atmosphere techniques.

The polymers were characterized by the following methods:

¹³C-NMR

The ¹³C-NMR analyses were performed on a Bruker DPX 400 MHz instrument,in tetrachlorodideuteroethane at 130° C.

Pn (Number Average Degree of Polymerization), evaluated by ¹H-NMRanalysis, gives a molecular weight measure for low molecular weightproducts, assuming one double bond per chain, as described by Resconi etal. (JACS, 120:2308-2321, 1998).

Viscosity Measurements

The intrinsic viscosity (I.V.) was measured in tetrahydronaphtalene(THN) at 135° C.

The polymer molecular weights were determined from the viscosity values.

IR Analysis

IR analysis were performed on a Nicolet 20 instrument, on samples of 0.1mm thickness.

DSC Analysis

The T_(g) values were measured on a DSC Mettler instrument. The sampleswere first heated to 200° C. at 20° C./min. then cooled to −120° C. at60° C./min. and finally heated to 200° C. at 20° C./min.

Catalyst Components

Methylalumoxane (MAO)

(1) A commercial (Witco, MW 1400) 10% w/w toluene solution of MAO (1.7M)was used as such.

(2) Alternatively, the commercial sample was dried in vacuum to afree-flowing powder (residual AlMe₃ about 3-5 mol %).

tris(2,4,4-Trimethyl-pentyl)aluminoxane (TIOAO)

tris(2,4,4-trimethyl-pentyl)aluminum (TIOA) was purchased from Witco andwas diluted to a 1M solution in hexane. 3.45 ml of said solution wereadded at room temperature to 5 ml of toluene, previously deoxygenatedand distilled over triisobutylaluminum. 0.031 ml of H₂O were then addedat room temperature with a syringe and the resulting solution wasstirred for 10 minutes at room temperature.

Catalyst Mixture

The catalyst mixture was prepared by adding the desired amount of themetallocene to the proper amount of MAO, thus obtaining a solution whichwas stirred for 10 minutes at room temperature and then injected intothe autoclave, at the polymerization temperature, in the presence of themonomer.

METALLOCENE SYNTHESIS Synthesis 1rac-Methylene-bis(1-methyl-4,5,6,7-tetrahydroinden-2yl)zirconiumDichloride

(a) Synthesis of bis(3-Methyl-2-indenyl)methane

In a 500 mL flask equipped with magnetic stirring bar were introduced14.8 g (0.114 moles) of 3-methyl-indene, 2.3 g (0.077 moles) ofpara-formaldehyde and 4.37 g (0.023 moles) of para-toluenesulphonic acidin 200 ml of toluene; the mixture was heated to 80° C. and wasmaintained under stirring for 1 hour at 80° C. Then the reaction wasquenched with water/NaHCO₃; the organic layer was separated, washed withwater and brought to dryness under reduced pressure. The crude productwas crystallized upon standing at room temperature, and then was furtherpurified by washing with pentane or MeOH, thus isolating 15.5 g ofbis(3-methyl-2-indenyl)methane (purity of 89.8% by G.C.; yield=89.8%).

The results of the ¹H-NMR analysis correspond to the ones reportedabove.

¹H NMR (CDCl₃): δ 7.2-7.5 (m, 8H); 3.73 (s, 2H); 3.35 (s, 4H); 2.29 (s,6H).

(b) Synthesis of rac-Methylene-bis(1-methyl-2-indenyl)zirconiumDichloride

6.5 g of bis(3-methyl-2-indenyl)methane (purity 90% by G.C., 21.5 mmol),obtained as reported above, were dissolved in 160 mL Et₂O, in a Schlenktube with magnetic stirring bar; the solution was cooled to −20° C. and27 mL of a 1.6 M solution of BuLi in hexane (43.2 mmol) were addeddropwise in 15 minutes. The obtained solution was allowed to warm toroom temperature and stirred for 5 hours, obtaining a red suspension,which was then cooled to −80° C. and added to a slurry of 5 g of ZrCl₄(MW =233.03, 21.4 mmol) in 160 mL of pentane, in a 500 mL flask, at −80°C. After warming to room temperature, the mixture was stirred overnight.The yellow suspension was dried to a free-flowing powder; said powderwas then washed with pentane (¹H-NMR analysis showed the presence ofboth rac- and meso-CH₂(1-Me-2-Ind)₂ZrCl₂), transferred into anextraction apparatus and finally extracted with refluxing CH₂C₂; ayellow precipitate formed in the collecting flask during the extraction.At the end of the extraction, CH₂Cl₂ was concentrated to 20 mL andfiltered. The residue was washed with Et₂O and pentane, and finallydried, to yield 2.98 g of yellow solid.

¹H NMR analysis showed the presence of the pure target productrac-CH₂(1-Me-2-Ind)₂ZrCl₂. ¹H NMR (CD₂Cl₂, ref. CDHCl₂ at 5.383 ppm,room temp.): Cp-CH₃, 2.535, s; CH₂, 4.375, s; Cp-H, 5.974, s; Ar,7.2-7.4, m; 7.5-7.6, m.

(c) Synthesis ofMethylene-bis(1-methyl-4,5,6,7-tetrahydroinden-2-yl)zirconium Dichloride

0.921 g of rac-CH₂(1-Me-2-Ind)₂ZrCl₂, obtained as reported above, 150 mgof PtO₂ and 80 mL of CH₂Cl₂ were placed in a 250 mL glass reactor with amagnetic stirring bar; nitrogen was purged with H₂ and the reactor waspressurized to 5.5 atm with H₂. The mixture was stirred at roomtemperature for 3 hours; the pressure was then released and the slurrywas filtered to remove PtO₂. The obtained residue was washed twice withCH₂Cl₂; the yellow-green solution of the filtrate, combined with thewashings, was concentrated in vacuo to give a foamy residue, which wasthen treated with Et₂O (5 mL), filtered and dried, to give 0.30 g of thetarget product, in the form of a green-gray powder (yield 32.4%).

¹H NMR (CD₂Cl₂, ref. CDHCl₂ at 5.377 ppm, room temp.): Cp-CH₃, 1.857, s;H₄Ind, 1.6-1.8, m, 2.3-2.6, m, 2.7-3.0, m; CH₂, 4.061, s; Cp-H, 5.057,s.

Synthesis 2Methylene-bis(1-t-butyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumDichloride

(a) Synthesis of bis(3-t-Butyl-2-indenyl)methane

In a 500 mL flask equipped with magnetic stirring bar were introduced12.35 g (0.072 moles) of 1-1-butyl-indene, 1.43 g (0.048 moles) ofpara-formaldehyde and 2.73 g (0.014 moles) of para-toluenesulphonic acidin 200 ml of toluene; the mixture was heated to 80° C. and wasmaintained under stirring for 6 hours at 80° C. Then the reaction wasquenched with water/NaHCO₃; the organic layer was separated, washed withwater and brought to dryness under reduced pressure. The crude productcrystallized upon standing at room temperature, and then was furtherpurified by washing with MeOH, thus isolating 10.8 gbis(3-t-butyl-2-indenyl)methane (purity of 90.9 by G.C.; yield=76.81%).

¹H NMR (CDCl₃): δ 7.6-7.8 (d, 2H); 7.1-7.4 (m, 6H); 4.23 (s, 2H); 3.34(s, 4H); 1.58 (s, 18H).

(b) Synthesis of Methylene-bis(1-t-butyl-2-indenyl)zirconium Dichloride

3 g of bis(3-t-butyl-2-indenyl)methane (purity 93.1% by G.C., 7.83mmol), obtained as reported above, were dissolved in 63 mL Et₂O, in aSchlenk tube with magnetic stirring bar; the solution was cooled to −80°C. and 10.6 mL of a 1.6 M solution of BuLi in hexane (16.96 mmol) wereadded dropwise in 15 minutes. The obtained solution was allowed to warmto room temperature and stirred for 5 hours, thus obtaining a redsuspension, which was then cooled to −80° C. and added to a slurry of1.96 g of ZrCl₄ (8.41 mmol), in 63 mL of pentane, in a 250 mL flask, at−80° C. After warming to room temperature, the mixture was stirredovernight. The yellow suspension was dried to a free-flowing powder. ¹HNMR analysis showed the presence of the target productrac-CH₂(1-t-Bu-2-Ind)₂ZrCl₂ as the only isomer. The powder was slurriedin 100 mL of CH₂Cl₂, transferred into an extraction apparatus andextracted with refluxing CH₂Cl₂ for 6 hours (a yellow precipitate formedin the collecting flask during the extraction). At the end of theextraction, CH₂Cl₂ was concentrated to 10 mL and then filtered. Theresidue was washed with pentane, until the washing was colorless, andwas dried to yield 1.757 g of a yellow solid. ¹H NMR analysis showed thepresence of the pure target product rac-CH₂(1-1-Bu-2-Ind)₂ZrCl₂.

¹H NMR (CD₂Cl₂, ref. CDHCl₂ at 5.377 ppm, room temp.): t-Bu, 1.719, s;CH₂, 4.926, s; Cp-H, 6.220, s; Ar, 7.2-7.3, m; 7.4-7.5, m, 7.8-7.9, m.

Additional 0.4 g of product were recovered from the filtrate, byrecrystallization from toluene and washing with Et₂O. The combined yieldwas 55%.

(c) Synthesis ofMethylene-bis(1-butyl-4,5,6,7-tetrahydroinden-2-yl)zirconium Dichloride

1.08 g of rac-CH₂(1-1-Bu-2-Ind)₂ZrCl₂, obtained as reported above, 150mg of PtO, and 100 mL of CH₂Cl₂ were placed in a 250 mL glass reactorwith a magnetic stirring bar; nitrogen was purged with H₂ and thereactor was pressurized to 5.5 atm with H₂. The obtained mixture wasstirred at room temperature for 3 hours; the pressure was then releasedand the slurry was filtered to remove PtO₂. The obtained residue waswashed twice with CH₂Cl₂; the yellow-green solution of the filtrate,combined with the washings, was concentrated in vacuo to give a greenfoamy residue, which was then treated with Et₂O (5 mL), filtered anddried, to give 0.26 g of the target product, in the form of a lightgreen powder (yield 24%).

¹H NMR (CD₂Cl₂, ref. CDHCl₂ at 5.377 ppm, room temp.): Cp-CH₃, 1.376, s;H₄Ind, 1.6-1.9, m, 2.4-2.6, m, 2.7-2.9, m, 2.9-3.1, m; CH₂, 4.627, s;Cp-H, 5.382, s.

Polymerization Tests EXAMPLES 1-2 AND COMPARATIVE EXAMPLE 1 PropyleneHomopolymerization

Propylene was charged at room temperature in a 1-L or 4.25-L jacketedstainless-steel autoclave, equipped with magnetically driven stirrer anda 35-ml stainless-steel vial, connected to a thermostat for temperaturecontrol, previously purified by washing with a AliBu₃ solution in hexaneand dried at 50° C. in a stream of propylene. AliBu₃ (1 mmol in hexane)was added as scavenger before the monomer.

The autoclave was then thermostatted at 2° C. below the polymerizationtemperature and then a toluene solution containing a mixture of catalystand cocatalyst, in the amounts reported in Table 1, was injected intothe autoclave, by means of nitrogen pressure through the stainless-steelvial. The temperature was rapidly raised to the polymerizationtemperature and the polymerization was performed at constant temperaturefor 1 hour.

After having vented the unreacted monomer and having cooled the reactorto room temperature, the polymer was dried under reduced pressure, at60° C.

The polymerization conditions and the characterization data of theobtained polymers are reported in Table 1; the polymers obtainedaccording to the present invention were all amorphous.

From the obtained results, it is evident that the catalysts containingthe bridged (4,5,6,7-tetrahydroinden-2-yl)metallocenes of the presentinvention are unexpectedly much more active than the correspondingbis-indenyl analogues; the prior art metallocene of Comparative Example1 turned out to be totally inactive.

EXAMPLES 3 AND 4 Ethylene Homopolymerization

A 1 L stainless-steel autoclave, equipped with magnetic stirrer,temperature indicator and feeding line for the ethylene, wasthermostatted with H₂O/steam and purified by purging with ethylene at80° C. Under ethylene purge, 500 mL of n-hexane and TIBA (2 mmol in Ex.3; 1 mmol in Ex. 4) were added; the temperature was brought to 80° C.and the reactor was vented to remove residual nitrogen. The reactor wasthen pressurized with ethylene up to 11 bar-a. The catalyst solution,comprising the catalyst and cocatalyst reported in Table 2A, wasinjected into the autoclave with ethylene overpressure and the ethylenepartial pressure was stabilized (Ptot=10 bar-g). Polymerization wascarried out at 80° C. for 1 hour, by maintaining a constant ethylenepartial pressure of 9.6 bar. The polymerization was interrupted bydegassing unreacted ethylene; after filtration and drying in vacuum at60° C.

The polymerization conditions and results are reported in Table 2A; thecharacterization data of the obtained polymers are indicated in Table2B.

From the results reported in Table 2B, it is evident that themetallocenes according to the present invention are able to yield linearα-olefins, having low values of Pn (Number Average Degree ofPolymerization) and having a number of terminal vinyl unsaturations upto 100% of the total number of terminal unsaturations. Therefore, byvarying the substitution pattern on the catalysts according to theinvention, it is possible to obtain linear α-olefins having very highpercentage of terminal vinyl unsaturations, thus providing PE waxeshaving low Pn.

EXAMPLES 5-6 AND COMPARATIVE EXAMPLES 2-3 Ethylene Homopolymerization

A 200 mL glass autoclave, provided with magnetic stirrer, temperatureindicator and feeding line for ethylene, was purified and fluxed withethylene at 35° C. At room temperature were introduced 90 ml of hexane.

The catalytic system was prepared separately in 10 ml of heptane byconsecutively introducing the cocatalyst reported in Table 2A and, after5 minutes under stirring,methylene-bis(1-t-butyl-4,5,6,7-tetrahydroinden-2-yl)zirconiumdichloride solved in the lowest possible amount of toluene.

After 5 minutes under stirring, the solution was introduced into theautoclave under ethylene flow; the reactor was closed and thetemperature risen to 80° C. The autoclave was then pressurized to 4.6barg and the total pressure was kept constant by feeding ethylene.

After the polymerization time reported in Table 2A, the reaction wasstopped by cooling and degassing the reactor, and by introducing 1 mlMeOH. The obtained polymer was washed with acidic MeOH, the with MeOHand finally dried under vacuum in oven at 60° C.

The polymerization conditions and results are reported in Table 2A; thecharacterization data of the obtained polymers are indicated in Table2B.

The polymer obtained in Comparative Example 2 was further characterizedby ¹³C-NMR analysis; it resulted that said polymer is a linear α-olefincontaining 0.15% of C₂ branches and 0.09% of C_(>6) branches.

From the results reported in Table 2A, it is evident that the bridgedbis(tetrahydro-indenyl)metallocenes according to the present inventionare unexpectedly much more active that the bridged bis-indenylanalogues.

The results of Table 2B clearly show that, by changing the substitutionpattern of the methylene-bridged metallocenes of the invention, it ispossible to obtain in high yields polyethylenes having intrinsicviscosity (I.V.) ranging from very low values to high values, thusallowing polymers having a wide range of molecular weights to beobtained.

EXAMPLES 7-10 Ethylene/Propylene Copolymerization

Copolymerization reactions were carried out in a 1-L jacketedstainless-steel autoclave, as described in Examples 1-2. AliBu₃ (1 mmolin hexane) and propylene (530 g, 1 L total volume at 60° C.) werecharged and thermostatted at 55° C.; the amounts of catalyst andcocatalyst reported in Table 3 were injected into the autoclave, bymeans of ethylene pressure (using the amount of ethylene required toachieve the bath composition shown in Table 3), through thestainless-steel vial. The temperature was rapidly raised to 50° C. andthe polymerization was carried out for 1 hour, at constant temperatureand monomer composition, by feeding the mixture of ethylene andpropylene reported in Table 3.

The polymerization was stopped with CO; the unreacted monomers werevented and the obtained copolymer was dried under reduced pressure, at60° C.

The polymerization conditions and the characterization data of theobtained copolymers are indicated in Table 3.

EXAMPLE 11 Ethylene Homopolymerization

The following polymerization procedure, similar to the one described inexamples 3 and 4 was followed: a 1 L stainless-steel autoclave equippedwith magnetic stirrer, temperature indicator and feeding line for theethylene, was thermostatted with H₂O/steam and purified by purging withethylene at 80° C. Under ethylene purge, 500 mL of n-hexane and 1 mmolof TIBA were charged into the reactor; the temperature was brought to80° C. and the reactor was vented to remove residual nitrogen. Thereactor was then pressurized with ethylene up to 11 bar-a. The catalystsolution, comprising the catalyst and cocatalyst reported in Table 2A,was injected into the autoclave with ethylene overpressure and theethylene partial pressure was stabilized (Ptot=10 bar-g). Polymerizationwas carried out at 80° C. for 1 hour, by maintaining a constant ethylenepartial pressure. The polymerization was interrupted by degassingunreacted ethylene; after filtration and drying in vacuum at 60° C.

The polymerization conditions and results are reported in Table 2A; thecharacterization data of the obtained polymers are indicated in Table 2Band Table 4. The GPC curve of the obtained is reported in FIG. 1A.

From the results reported in Table 2B, it is evident that themetallocenes according to the present invention are able to yield linearα-olefins, having low values of Pn (Number Average Degree ofPolymerization) and having a number of terminal vinyl unsaturations upto 100% of the total number of terminal unsaturations.

COMPARATIVE EXAMPLE 4 Ethylene Homopolymerization With a Prior ArtMetallocene

The polymerization procedure described in Example 11 was repeated, withthe only difference that the catalytic system used was obtained byadding 0.14 ml of MAO solution (1.7M in toluene, 0.24 mmol Al) to 0.25mg of rac-Me₂C(3-iPr-Ind)₂ZrCl₂ (0.48 μmol) dissolved in 2.5 mL oftoluene (Al/Zr=500), and aging the mixture 10 minutes.

The polymerization yielded polyethylene with an activity of 38kgPE/g_(cat).h; characterization data of the obtained polymer areindicated in Table 4. The GPC curve of the obtained is reported in FIG.1B.

EXAMPLE 12 Preparation of Bimodal Polyethylene

1 L stainless-steel autoclave, thermostatted with H₂O/steam and purifiedby purging with ethylene at 80° C. Under ethylene purge, 540 mLtechnical hexane and 1 mmol TIBA were charged into the reactor, thetemperature was brought to 80° C. and the reactor was vented to removeresidual nitrogen, then pressurized with ethylene up to 9.5 bar-g.

0.17 mL of MAO solution (1.7 M in toluene, 0.28 mmol Al) were added to0.25 mg of rac-CH₂(1-Me-2-H₄Ind)₂ZrCl₂ (0.57 μmol) dissolved in 1.2 mLof toluene (Al/Zr=500) and aged 10 min.

0.14 mL of MAO solution (1.7 M in toluene, 0.24 mmol Al) were added to0.25 mg of rac-Me₂C(3-iPr-Ind)₂ZrCl₂ (0.48 μmol) dissolved in 2.5 mL oftoluene (Al/Zr=500) and aged 10 min.

The two catalyst/cocatalyst mixtures were combined, siphoned into thesteel vial and injected into the reactor by means of ethyleneoverpressure, the ethylene partial pressure was then stabilized to 9.6bar-a, (P_(tot) 11 bar-a). The test was carried out at 80° C. for 30 minhour, by maintaining a constant ethylene partial pressure. Afterquenching the reaction with CO and degassing unreacted ethylene, thepolymer was isolated by filtration and dried in vacuo at 60° C., thusobtaining 23.5 g of polyethylene, having a solubility in cold xylene of0.3% wt; characterization data of the obtained polymer are indicated inTable 4. The GPC curve of the obtained is reported in FIG. 1C.

The diagrams reported in FIG. 1 clearly demonstrate that, by combiningthe metallocene rac-CH₂(1-Me-2-H₄Ind)₂ZrCl₂ of the invention, able togive PE waxes, and the prior art metallocene rac-Me₂C(3-iPr-Ind)₂ZrCl₂able to give PE of higher molecular weight, it is possible to producepolyethylene polymers with a well-defined bimodal distribution.

TABLE 1 Propylene homopolymerization Metallocene MAO Al/Zr T YieldActivity I.V. Ex. Type (μmol) (mmol) (mol) (° C.) (g) (kg/gCat.h) Mw(dl/g) 1 r-CH₂(1-tBut-2-tetrahydro-Ind)₂ZrCl₂ 0.38 (1) 1.14 3000 50138.01 690.1 72,000 0.7 2 r-CH₂(1-tBut-2-tetrahydro-Ind)₂ZrCl₂ 0.57 (1)1.72 3000 30 12.57 41.9 178,000 1.37 Comp. 1 CH₂(2-Ind)₂ZrCl₂ 4.94 (2)7.41 1500 50 0 INACTIVE — — (1) Commercial 10% w/w toluene solution ofMAO (1.7M; Witco). (2) The commercial sample (1) was dried in vacuum toa free-flowing powder (residual AlMe₃ about 3-5 mol %).

TABLE 2A Ethylene homopolymerization Cocatalyst Metallocene Al/Zr TimeYield Activity Example Type mg Type (mmol) (mol) (min) (g) (Kg/gCat.h) 3 r-CH₂(1-Me-2-tetrahydro-Ind)₂ZrCl₂ 0.2 MAO (1) 0.23 500 60 14.0 70.0 4 r-CH₂(1-t-But-2-tetrahydro-Ind)₂ZrCl₂ 0.2 MAO (1) 0.86 3000 60 32.1214.0  5 r-CH₂(1-t-But-2-tetrahydro-Ind)₂ZrCl₂ 0.12 MAO (1) 0.24 1000 21.2 1724.6  6 r-CH₂(1-t-But-2-tetrahydro-Ind)₂ZrCl₂ 0.1 TIOAO 0.2 1000 60.71 408.2 11 r-CH₂(1-Me-2-tetrahydro-Ind)₂ZrCl₂ 0.5 MAO (1) 0.57 500 6026.0 52.0 Comp. 2 CH₂(2-Ind)₂ZrCl₂ 0.3 MAO (2) 0.75 1000 10 1.51 132.6Comp. 3 CH₂(2-Ind)₂ZrCl₂ 0.5 TIOAO 2.50 2000 30 1.54 27.1 (1) Commercial10% w/w toluene solution of MAO (1.7M; Witco). (2) The commercial sample(1) was dried in vacuum to a free-flowing powder (residual AlMe₃ about3-5 mol %).

TABLE 2B Ethylene homopolymerization Terminal vinyl I.V. ΔH T_(m)unsaturations Terminal vinylidene Example (dl/g) M_(v) Pn (J/g) (° C.)(%) unsaturations (%)  3 0.42 15,800 304 208 140 100 0  4 4.99 480,0008540 n.d. n.d. n.d. n.d.  5 4.42 405,300 n.d. n.d. n.d. n.d. n.d. 6 >8 >900,000 n.d. n.d. n.d. n.d. n.d. 11 0.41 15300 304 242 131 100 0Comp. 2 0.17 4530 81 217 125 91.5 8.5 Comp. 3 0.2 n.d. n.d. n.d. n.d.n.d. n.d.

TABLE 3 Ethylene/propylene copolymerization Metallocene MAO Al/Zr C₃bath C₂ bath C₃ feed C₂ feed Yield Activity C2 I.V. Tg Ex. Type μmol(mmol) (mol) (g) (g) (g) (g) (g) (Kg/gCat.h) (% wt) (dl/g) (° C.)  7r-CH₂(1-t-Bu-2-tetrahydro-Ind)₂ZrCl₂ 0.95 (1) 2.86 3000 314 3.4 0.0 0.016.98 34.0 5.0 0.68 −7  8 r-CH₂(1-t-Bu-2-tetrahydro-Ind)₂ZrCl₂ 0.48 (1)1.43 3000 311 6.8 0.0 20.3 63.99 255.9 11.2 1.28 −24  9r-CH₂(1-t-Bu-2-tetrahydro-Ind)₂ZrCl₂ 0.38 (1) 1.14 3000 294 21.7 2.712.8 67.61 338.1 36.6 1.61 −31 10 r-CH₂(1-t-Bu-2-tetrahydro-Ind)₂ZrCl₂0.38 (1) 1.14 3000 303 49.3 13.2 20.6 36.01 180.1 67.5 3.63 −35 (1)Commercial 10% w/w toluene solution of MAO (1.7M; Witco).

TABLE 4 Ethylene homopolymerization Activity I.V. Example Metallocene(Kg/g_(Cat).h) (dl/g) M_(w) M_(n) M_(w)/M_(n) Comp. 4rac-Me₂C(3-iPr-Ind)₂ZrCl₂ 38.0 6.9 580,500 244,700 2.4 11rac-CH₂(1-Me-2-H₄Ind)₂ZrCl₂ 52.0 0.41 18,000 38,900 2.8 12rac-Me₂C(3-iPr-Ind)₂ZrCl₂ + 94.0 4.44 433,000 23,100 18.8rac-CH₂(1-Me-2-H₄Ind)₂ZrCl₂ bimodal

What is claimed is:
 1. A bridged bis(tetrahydro-indenyl)metallocene offormula (I):

wherein: M is a transition metal belonging to group 3, 4, 5, 6 or to thelanthanide or actinide groups of the Periodic Table of the Elements; thesubstituents X, the same or different from each other, are monoanionicsigma ligands selected from the group consisting of hydrogen, halogen,—R, —OR, —OSO₂CF₃, —OCOR, —SR, —NR₂ and —PR₂ groups, wherein the Rsubstituents are linear or branched, saturated or unsaturated, C₁-C₂₀alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl or C₇-C₂₀arylalkyl radicals, optionally containing one or more atoms belonging togroups 13-17 of the Periodic Table of the Elements, and two Rsubstituents may form a 5-7 membered ring; (ZR¹ _(i))_(j) is a divalentgroup bridging the two tetrahydro-indenyl residues, Z being selectedfrom the group consisting of C, Si, Ge, N and P; the substituents R¹,the same or different from each other, are selected from the groupconsisting of hydrogen, linear or branched, saturated or unsaturatedC₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl andC₇-C₂₀ arylalkyl radicals, optionally containing one or more atomsbelonging to groups 13-17 of the Periodic Table of the Elements; thesubstituents R² and R³, the same or different from each other, areselected from the group consisting of halogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals, optionally containingone or more atoms belonging to groups 13-17 of the Periodic Table of theElements, —OR, —SR, —NR₂, N-pyrrolyl, N-indolyl, —PR₂, —BR₂ and —SiR₃groups, wherein the R substituents have the meaning reported above; ortwo adjacent R³ substituents form a ring having from 4 to 8 carbonatoms; p is an integer ranging from 0 to 3, being equal to the oxidationstate of the metal M minus 2; i is 1 or 2; j is an integer ranging from1 to 4; m is an integer ranging from 1 to 2; and n is an integer rangingfrom 0 to
 8. 2. The bridged bis(tetrahydro-indenyl)metallocene accordingto claim 1, wherein said metal M is Zr or Hf.
 3. The bridgedbis(tetrahydro-indenyl)metallocene according to claim 1 or 2, whereinsaid X substituents are Cl, Br or methyl.
 4. The bridgedbis(tetrahydro-indenyl)metallocene according to claim 1, wherein (ZR¹_(i))_(j) is selected from the group consisting of CR₂, SiR¹ ₂, GeR₂,NR¹, PR¹ and (CR¹ ₂)₂.
 5. The bridged bis(tetrahydro-indenyl)metalloceneaccording to claim 4, wherein (ZR¹ _(i))_(j) is selected from the groupconsisting of Si(CH₃)₂, SiPh₂, CH₂, (CH₂)₂ and C(CH₃)₂.
 6. The bridgedbis(tetrahydro-indenyl)metallocene according to claim 1, wherein R² isselected from the group consisting of methyl, ethyl, n-propyl, i-propyl,n-butyl, t-butyl, phenyl, benzyl and trimethyl-silyl; and R³ is selectedform the group consisting of halogen, methyl, ethyl, n-propyl, i-propyl,n-butyl, t-butyl, phenyl and benzyl.
 7. A catalyst for thepolymerization of olefins comprising the product obtained by contacting:(A) one or more bridged bis(tetrahydro-indenyl)metallocenes of formula(I):

 wherein: M is a transition metal belonging to group 3, 4, 5, 6 or tothe lanthanide or actinide groups of the Periodic Table of the Elements;the substituents X, the same or different from each other, aremonoanionic sigma ligands selected from the group consisting ofhydrogen, halogen, —R, —OR, —OSO₂CF₃, —OCOR, —SR, —NR₂ and —PR₂ groups,wherein the R substituents are linear or branched, saturated orunsaturated, C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl, C₇-C₂₀alkylaryl or C₇-C₂₀ arylalkyl radicals, optionally containing one ormore atoms belonging to groups 13-17 of the Periodic Table of theElements, and two R substituents may form a 5-7 membered ring; (ZR¹_(i))_(j) is a divalent group bridging the two tetrahydro-indenylresidues, Z being selected from the group consisting of C, Si, Ge, N andP; the substituents R¹, the same or different from each other, areselected from the group consisting of hydrogen, linear or branched,saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl, C₆-C₂₀ aryl,C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals, optionally containingone or more atoms belonging to groups 13-17 of the Periodic Table of theElements; the substituents R² and R³, the same or different from eachother, are selected from the group consisting of halogen, linear orbranched, saturated or unsaturated C₁-C₂₀ alkyl, C₃-C₂₀ cycloalkyl,C₆-C₂₀ aryl, C₇-C₂₀ alkylaryl and C₇-C₂₀ arylalkyl radicals, optionallycontaining one or more atoms belonging to groups 13-17 of the PeriodicTable of the Elements, —OR, —SR, —NR₂, N-pyrrolyl, N-indolyl, —PR₂, —BR₂and —SiR₃ groups, wherein the R substituents have the meaning reportedabove; or two adjacent R³ substituents form a ring having from 4 to 8carbon atoms; p is an integer ranging from 0 to 3, being equal to theoxidation state of the metal M minus 2; i is 1 or 2; j is an integerranging from 1 to 4; m is an integer ranging from 1 to 2; n is aninteger ranging from 0 to 8; and (B) a suitable activating cocatalyst.8. The catalyst according to claim 7, wherein said activating cocatalystis at least one of an alumoxane and a compound that forms analkylmetallocene cation.
 9. A process for the polymerization of olefinscomprising the polymerization reaction of one or more olefinic monomersin the presence of a catalyst as described in claim 7 or
 8. 10. Theprocess according to claim 9, wherein said olefinic monomer is selectedfrom the group consisting of ethylene, propylene, 1-butene, 1-hexene,4-methyl-1-pentene, 1-octene and mixtures thereof.
 11. The processaccording to claim 10, for the production of atactic propyleneoligomers, terminated with vinylidene end-groups.
 12. The processaccording to claim 10, for the production of ethylene linear α-olefinshaving Pn ranging from 50 to 500, wherein more than 95% of theunsaturations are terminal vinyl unsaturations.